Silencer with outer housing contacting inner conduit to define resonance chambers



J. C. WALKER SILENOER WITH OUTER HOUSING CONTACTING INNER CONDUIT TODEFINE RESONANCE CHAMBERS Original Filed Oct. 24, 1963 W INVENTOR. IJ0/?77 6' li d/Zar Dec. 6, 1966 III/llll'lllu'llllllllllll United StatesPatent SILENCER WITH OUTER HOUSING CONTACTING INNER CONDUIT T0 DEFINERESONANCE CHAMBERS John C. Walker, Jackson, Mich, assignor to WalkerManufacturing Company, a corporation of Delaware Continuation ofapplication Ser. No. 318,652, Oct. 24,

1963. This application Oct. 4, 1965, Ser. No. 496,240 23 Claims. (Cl.18148) My invention relates to gas silencing devices and, in particular,concerns a silencing device that is useful in the exhaust systems ofautomotive internal combustion engines and is a continuation of mycopending patent application, Serial No. 318,652, filed October 24,1963, now abandoned.

It is an object of my invention to provide a silencing device that maybe readily manufactured, which silences more than one frequency or typeof noise, and which is adapted for use in an automotive exhaust systemdeveloped by the assignee hereof wherein a multiplicity of small sizesilencing components are distributed over the entire length of thesystem.

Another object of the invention is to provide a silencer that may beused in conjunction with a more or less conventional muffier to providebetter performance than a resonator type muffler.

The invention accomplishes the foregoing and other objects by means of asimple, essentially two-part assembly of perforated gas flow conduit andhousing which is formed so as to provide a series of spit chambers and aquarter wave length or quincke tuning chamber.

A preferred form of the invention is illustrated in the accompanyingdrawings in which:

FIGURE 1 is an end view taken from the left of FIGURE 2;

FIGURE 2 is a top elevation of the structure of FIGURE 1 on a reducedscale, partly broken away, and with an inlet bushing shown in phantomlines;

FIGURE 3 is an enlarged section along the line 33 of FIGURE 2;

FIGURE 4 is a section along the line 4 4 of FIG- URE 3; and

FIGURE 5 is a cross-section similar to FIGURE 3 of a modified form ofthe invention.

The silencing device 1 has a housing 3 that is formed of an open-endedtube of double wrap construction, i.e., comprises a layer of metalwrapped upon itself in helical fashion, to form a two layer, sounddeadened sheet and spotwelded together at the three layer joint 5. Ifdesired, the housing could be a double layer construction formed of twodifferent tubes, one inside the other, such as stainless steel inside ofaluminized steel for optimum corrosion resistance. The housing 3 isprefera'bly of the generally rectangular shape illustrated and runningsubstantially the full length of it, and in contact with opposite sidesof it, is a lowered gas conveying tube 7 which may be of lock-seam (notshown) construction.

In the embodiment illustrated, the tube 7 is offset from the center lineof the housing 3 and forms a chamber 9 with the side 11 of the housing3. Chamber 9 runs the full length of the housing 3 in the formillustrated but it may be made shorter if desired. A bank of louvers 13,adjacent the inlet end of the tube 7 provides an accoustic couplingwit-h the chamber 9 and by properly selecting the length of the chamber9 in proper relationship to the frequency to be silenced, it may be usedto act as a quincke or quarter wave tuning tube. In the case, thedistance from the downstream end of the bank of louvers 13 to thedownstream end ICC of chamber 9 would be one-quarter of the wave lengthof the frequency to be silenced subject to such adjustments as may seemdesirable to obtain maximum silencing effect. For example, in oneapplication the theoretical quarter Wave length was 41 inches but thebest total silencing in the system was obtained with a length of 37inches.

The use of flat louvers as the communication with the chamber 9 givessome anti-roughness or high frequency attenuating effect. However, it ispossible to use one large or several small openings at either end of thetube 7 or to use other types of communication between tube 7 and chamber9, various such forms of acoustic connection being known in the art. Thebank of louvers 13 should be located as close as possible in the exhaustsystem to an antinode of the frequency to be silenced, preferably thefirst antinode.

By offsetting the tube 7 from the center line of the housing 3, thechamber 9 is made larger for a given size housing 3 than would be thecase if the tube were on center. This gives a larger volume and crosssectional area to the chamber 9 which may be desired in someapplications.

The space inside housing 3 on the other side of the conduit from chamber9 is divided into a series of separate spit chambers which communicatewith the inside of the pipe 7 through banks of louvers 15 which may bethe flat type but are preferably the round type. The opposite sides ofthe tube 7 that are in contact with the shell 3 may be spot-welded to itas indicated at 17. The various spit chambers 19 can be formed bypinching down sections 21 of the housing 3 into surface contact wit-hone side of the tube 7, the metal being gathered into four layerreversely bent bites or folds 23 that may be spot-welded together. Thespit chambers 19 pass low and medium frequencies and act to take outroughness and high frequency sounds. The lengths of the respective spitchambers can be varied by spacing the pinches 23 and the number oflouvers and rows of louvers in them can be varied among the spitchambers, thus providing a varying attenuation to cover a wider range ofsound than if the chambers are all uniform.

The opposite ends of the shell 3 are closed by being pinched down asindicated at 25. These ends are fastened together in some manner toprevent leakage of gas, such as by aircwelding. Preferably, inlet andoutlet bushings 27 of the type normally used in muffier manufacturingare inserted between the tube 7 and the housing 'at opposite ends toprovide a means for attachment to other components in an exhaustsilencing system. If desired, however, the inner tube 7 may be extendedout of one or both ends to provide the attachment bushings.

In use, gas flow through the tube 7 will be subject to the silencingeffect of the series of spit chambers 19 on the one side and the quinckechamber 9 ion the other side.

The structure illustrated is capable of substantial modification,especially with respect to the number and size of chambers 19 and 9. Oneor more spit chambers could be put on the same side as chamber 9 byusing the pinch down technique 21. Of course, that side of the conduit 7in such spit chambers would then be perforated or louvered. Aspreviously indicated, the bank of louvers 13 is preferred but otheropenings may be used and they may be located at the outlet end or suchother point along the length of chamber 9 as may be desired. If desire,instead of spit chambers 19, a sec-0nd independent quincke or quarterwave length chamber may be formed on that side of the conduit 7 in whichcase limited communication will be provided between the conduit 7 andsuch chamber. The opposite modification is also possible, i.e., form allspit chambers on both sides of the tube 7 by pinching down at desiredpoints on each side. Two or more quincke chambers could be provided onone side by :using the pinch down technique 21. If a single wrap shell 3is used, the ends may be swaged down into contact with the inlet andoutlet bushings and the tube 7 instead of using the pinched joints at25. In a silencing system, one or more of these units of same ordifferent sizes may be employed and it will be seen that the unit 1 canbe bent after it has been assemble-d. Bending in some cases maybefacilitated by disposing the pinched sections 21 at differentadvantageous angles.

FIGURE shows a modified silencer 101 in Which the cross-sectional areaof the two longitudinal chambers 103 and 105 on opposite sides of thecenter tube 107 is increased so as to give more chamber volume and morearea for louver openings, as indicated by arcs L. The center tube 107and shell 109 are shown as concentric but they could be offset as shownin FIG- URES 1-4.

In the silencer 101 the shell 109 is substantially higher than centertube 107 but longitudinal inwardly extending channels 111 and 113 areformed in the top and sides of it to engage and be spotwelde-d at x tothe top and bottom of the tube 107 along the full length that the twoare coextensive. Otherwise, the silencer 101 may be of the sameconstruction as the unit 1 previously described. Thus, pinched downfolds 115 may be formed on one side of the shell to divide the chamber103 into a series of short length spit chambers corresponding tochambers 19.

Modifications may be made in the structure illustrated without departingfrom the spirit and scope of the invention.

What is claimed is:

1. A gas silencing device for silencing a note having a predeterminedfrequency comprising an elongated housing, a conduit inside the housingand extending substantially the full length thereof, said conduit beingsubstantially less in width than said housing, opposite sides of saidconduit being in engagement with opposite sides of the housing to dividethe housing into two longitudinal spaces separated by said conduit, thefirst of said spaces extending over a substantial part of the length ofthe housing, said conduit having a wall with a perforate portion openinginto said first space and said first space being substantially onequarter the wave length of said note whereby said first space acts as aquarter wave length tuning chamber for said note, the side of saidhousing over the second of said spaces having inwardly extendingportions at a plurality of sections in engagement with one side of saidconduit to divide said second space into a series of separate chambers,said conduit having perforate areas opening into each of said series ofseparate chambers whereby said chambers act as a series of spit chambersto silence high frequencies and roughness in the gas.

2. The invention set forth in claim 1 wherein the gas conduit is offsetfrom the center line of the housing so that one of said two spaces islarger than the other.

3. The invention set forth in claim 1 wherein said housing is providedwith said series of spit chambers by means of sections of opposite sidesextending inwardly into contact with the conduit and one side of theconduit with folds extending radially to the conduit.

4. The invention set forth in claim 3 wherein the opposite ends of thehousing extend inwardly so that opposite sides thereof are in contactwith each other and with the full circumference of said conduit.

5. The invention set forth in claim 1 where-in said housing is ofsubstantially the same height as the conduit.

6. The invention set forth in claim 1 wherein said housing issubstantially higher than said tube and has inwardly extendinglongitudinal channels formed therein to engage opposite sides of saidconduit.

7. The invention set forth in claim 1 wherein said housing comprises alaminate of two layers of metal.

8. The invention set forth in claim 1 wherein the perforate portioncomprises means defining a plurality of openings.

9. The invention set forth in claim 1 wherein said perforate portioncomprises a bank of louvers.

10. The invention set forth in claim 9 wherein the distance from thelouvers in said louver bank closest to said tuning chamber to the remoteend of said tuning chamber is approximately one quarter of the Wavelength of said note.

11. The invention set forth in claim 9 wherein said housing comprises atwo layer metal laminated shell.

12. The invention set forth in claim 9 wherein said tube and housing aresubstantially the same height.

13. The invention set forth in claim 9 wherein said housing is ofgreater height than said tube and has inwardly extending longitudinalchannels formed on opposite sides thereof to contact the top and bottomof said tube.

14. A gas silencing device for silencing a note having a predeterminedfrequency comprising a straight through gas fiow tube, a housing aroundthe outside of the tube but in contact with the top and bottom of thetube whereby it is divided into first and second separate longitudinalspaces located on opposite sides of the tube, said tube being perforatedon opposite sides to open into each of said spaces whereby said spacesact as silencing chambers, said tube being perforated only near one endof the first space and said first space being substantially as long as aquarter wave length of said note.

15. The invention set forth in claim 14 including means dividing thesecond of said spaces into a series of spit chambers.

16. A gas silencing device for attenuating a note having a predeterminedfrequency comprising a tubular housing having a long chamber therein anda plurality of small chambers therein, said long chamber having a lengthsubstantially equal to one quarter wave length of said note, a gas fiowtube running through the housing and having an inlet and an outlet end,an opening in the tube adjacent an end thereof into said long chamberwhereby it comprises a tuned chamber, and openings in the tube into eachof the small chambers whereby they comprise spit chambers.

17. A gas silencing device comprising a straight through gas flow tube,a continuous housing extending around said flow tube and contacting saidtube on opposite sides thereof, said housing being closed at oppositeends thereof and being in engagement with said tube along its containedlength on opposite sides thereof to define first and second longitudinaltuning chambers on opposite sides of said tube, and at least one openingthrough said tube into each of said chambers for silencing the gas flow,one of said chambers being adapted to silence at note having apredetermined frequency and the opening into said one chamber is spacedsubstantially one quarter of the wave length of said note from at leastone end of said one chamber.

18. A gas silencing device as set forth in claim 17 wherein the openinginto the one chamber is formed adjacent one end of said one chamber.

19. A gas silencing device comprising a straight through gas flow tube,a housing positioned around said tube, said housing being in engagementwith said tube on opposite sides thereof and spaced from said tubebetween the points of contact to define separate chambers on oppositesides of said tube, means forming closures for opposite ends of each ofsaid spaces, said last named means being effective to provide adifferent volume in one of said spaces than in the other of said spaces,and at least one opening through said tube into each of said spaces forsilencing gas flow.

20. A gas silencing device as set forth in claim 19 wherein the openinginto one of the spaces comprises a References Cited by the Examinerlouvered portion of the tube. UNIT D A E PATENT 21. A gas silencingdevice as set forth in claim 20 E ST T S 8 wherein the one space isadapted to silence a note of a 1,874,326 8/1932 Mason 18148 Xpredetermined frequency and the distance from the-lou- 5 2,027,359 1/1936 Wo d t a 9 vered portion to one end of the space is substantially2,367,473 1/1945 Smith 18148 equal to one quarter of the wave length ofsaid note. 3,128,841 4/ 1964 ll l W t al- Isl-+59 22. A gas silencingdevice as set forth in claim 21 wherein the louvered portion ispositioned adjacent the FOREIGN PATENTS end 0f the (me SPace- 10 892,7803/1962 Great Britain.

23. A gas silencing device as set forth in claim 19 further includingmeans for dividing the space at one side RICHARD B WILKINSON Primal,Examiner of the tube into a plurality of separate longitudinally yspaced chambers, there being at least one opening R. S. WARD, AssistantExaminer. through said tube into each of said chambers. 15

1. A GAS SILENCING DEVICE FOR SILENCING A NOT HAVING A PREDETERMINEDFREQUENCY COMPRISING AN ELONGATED HOUSING, A CONDUIT INSIDE THE HOUSINGAND EXTENDING SUBSTANTIALLY THE FUEL LENGTH THEREOF, SAID CONDUIT BEINGSUBSTANTIALLY LESS IN WIDTH THAN SAID HOUSING, OPPOSITE SIDES OF SAIDCONDUIT BEING IN ENGAGEMENT WITH OPPOSITE SIDES OF THE HOUSING TO DRIVETHE HOUSING INTO TWO LONGITUDIANAL SPACES SEPARATED BY SAID CONDUIT, THEFIRST OF SAID SPACES EXTENDING OVER A SUBSTANTIAL PART OF THE LENGTH OFTHE HOUSING, SAID CONDUIT HAVING A WALL WITH A PERFORATE PORTION OPENINGINTO SAID FIRST SPACE AND SAID FIRST SPACE BEING SUBSTANTIALLY ONEQUARTER THE WAVE LENGTH OF SAID NOT WHEREBY SAID FIRST SPACE ACTS AS AQUARTER WAVE LENGTH TURNING CHAMBER FOR SAID NOTE, THE SIDE OF SAIDHOUSING OVER THE SECOND OF SAID SPACES HAVING INWARDLY EXTENDINGPORTIONS AT A PLURALITY OF SECTIONS IN ENGAGEMENT WITH ONE SIDE OF SAIDCONDUIT TO DIVIDE SAID SECOND SPACE INTO A SERIES OF SEPARATE CHAMBERS,SAID CONDUIT HAVING PERFORATE AREAS OPENING INTO EACH OF SAID SERIES OFSEPARATE CHAMBERS WHEREBY SAID CHAMBERS ACT AS A SERIES OF SPIT CHAMBERSTO SILENCE HIGH FREQUENCIES AND ROUGHNESS IN THE GAS.